In organic chemistry, methenium (also called methylium, the methyl cation, or protonated methylene) is a positive ion with the formula . It can be viewed as a methylene radical (:) with an added proton , or as a methyl radical (•) with one electron removed. It is a carbocation and an enium ion, making it the simplest of the carbenium ions.

In organic chemistry, methenium (also called methylium, the methyl cation, or protonated methylene) is a positive ion with the formula . It can be viewed as a methylene radical (:) with an added proton , or as a methyl radical (•) with one electron removed. It is a carbocation and an enium ion, making it the simplest of the carbenium ions.